Recombination and complementation between R factors in Escherichia coli K12

Abstract

Recombination between chloramphenicol-sensitive (Cms) mutants of Rl, and R100, has been demonstrated in Escherichia coli K12 rec+; it occurs at reduced frequency in recB and recC, and is not detectable in reeA, indicating that R factor recombination depends on host functions. Some mutants of R1 also recombine with an R100 mutant in a similar way. recA cells carrying an R1 and an R100 Cms mutant (hetero-R state) have a low level of chloramphenicol-resistance, and form a chloramphenicol acetyl transferase that has lower specific activity than enzyme from hosts carrying wild-type or recombinant factors. These results suggest the occurrence of interallelic complementation between mutant R factors.